Associations between pharmaceutical contaminants, parasite load and health status in brown trout exposed to sewage effluent in a small stream

Owing to their widespread use, pharmaceuticals have become important pollutants of the aquatic environment. Pharmaceuticals and parasites can affect the immunity, physiology and behaviour of target organisms, both singly and through interaction. In this study, we related pharmaceutical concentration, parasite infection and condition in brown trout (Salmo trutta m. fario) collected at localities upstream and downstream of a sewage treatment plant (STP). The sites were separated by a weir preventing fish migration. Pharmaceutical number and concentrations differed significantly between sites. Antibiotics and antidepressants were found at the highest concentrations at both localities. Though fish condition and overall parasite abundance did not differ between sites, there was a significant difference in parasite community composition. A higher abundance of monogenean ectoparasites, along with a lower abundance of endoparasites, was observed at the downstream locality. The adverse effect of pharmaceutical load on ecto- and endoparasitic species on brown trout was further confirmed at the individual level using multivariate analysis. Both the number and concentration of pharmaceuticals in fish tissues reflected their high incidence in the environment, confirming the ability of trout to bioaccumulate pharmaceuticals. This could have important consequences on fish health, particularly in small streams where STP effluent represents a high proportion of stream flow. (C) 2020 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

The study found that pharmaceutical and parasite pollution have significant impacts on fish health and parasite community composition, adversely affecting the ectoparasites and endoparasites on brown trout. Differences in pharmaceutical concentration and types were observed between sites, while fish condition and overall parasite abundance did not differ significantly.